The present invention relates generally to impact-absorbing covering for traffic-carrying surfaces. More particularly, this invention relates to static structures having two area moments of inertia so that they can effectively absorb impact during falls but remain substantially rigid under normal loading.
By way of background, falls represent the leading cause of non-fatal injuries in the United States (Cost of Injury, 1989). In 1985, falls accounted for an estimated 21% of non-hospitalized injured persons (11.5 million people) and 33% of hospitalized injured persons (783,000 hospitalizations). In addition 9% of fatalities (12,866 deaths) were related to falls.
A number of epidemiological studies report a drastic increase of fall incidence rate in the elderly population over the age of 65, suggesting a direct relationship between aging and the frequency of fall events (Sorock, 1988; Healthy People 2000, 1990; Injury Prevention: Meeting the Challenge, 1989; National Safety Council, 1990; Grisso et al., 1990; DeVito et al., 1988; Waller, 1985; Waller, 1978; Sattin et at., 1990). In the age group above 65, the exact incidence of non-fatal falls is difficult to determine, but it has been estimated that approximately 30% of all individuals over the age of 65 have at least one fall per year (Sorock, 1988).
This represents a significant health problem when one considers the dramatic growth in the number of people over 65 and their proportion in the population. This age group currently makes up 12.5% of the U.S. population with projected increases to 19.5% by the year 2025 (A Profile of Older Americans: 1990, 1990). Of particular note is the growth of the "oldest old", those people over 75. In the decade between 1990 and 2000, the greatest growth in the over 55 age group will be among the 75 and older--an increase of 26.2 percent or a gain of nearly 4.5 million (U.S. Dept. of Commerce, Bureau of Census, 1988).
It was stated in Injury in America (1985, p. 43) that "Almost no current research deals with the mechanisms and prevention of injury from falls (the leading cause of non-fatal injury) . . . Little is known about the effectiveness of energy-absorbing materials, either worn by persons at high risk or incorporated in the surfaces onto which they fall".
Current approaches to solving the problem of injury from falls can be separated into two broad categories. The first category includes a harness device which is worn by the subject and tethered to a ceiling mounted track. If a person falls, the device lowers them to the ground in a controlled manner. While preliminary results have proven the system successful, it does have a number of drawbacks. The device must be worn by all potential fall victims to be effective and may require extensive modification of the existing architecture for the system to work between rooms.
Other devices in this category are either active or passive systems worn on critical impact regions of the body. The active system senses a fall and inflates air bags around the hips and knees while the passive devices employ an air bag or pad strapped to the hip region. Unfortunately these approaches only offer protection to the targeted areas and typically hands, wrists etc. will be unprotected during forward falls. A major disadvantage of all the devices in this first category is that they require significant effort on the part of the user and it is widely accepted that as the amount of individual effort required increases, the proportion of the population who will properly apply the system decreases (Injury in America, 1985).
The second category covers devices which use composite matting to absorb energy resulting from patient/floor impact during falls. U.S. Pat. Nos. 3,636,577, 4,557,475, 4,727,697, 4,846,457, 4,948,116, 4,991,834 and 4,998,717, all describe impact absorbing coverings which utilize air-filled cells or compressible materials to absorb the energy of a fall. Because these systems must be compliant to absorb energy, shoe/foot contact results in relatively large mat deflections under normal locomotion. This has the potential to increase the likelihood of falls due to toe/mat interference during foot swing. This factor would be greatly magnified in a nursing home setting, where many residents have an unsteady gait.
The present invention overcomes the above-described disadvantages inherent with various apparatuses and methods of the prior art. The invention presents a flooring system which requires no special clothing or restriction of movement since the floor will act as the injury prevention system. The design incorporates dually stiff flooring which would remain rigid under normal locomotion and would only deflect under impact loading. This approach offers a novel and effective system to reduce injuries from falls without leading to an increase in the fall rate.